This set of multiple-choice questions covers basic economic concepts like GDP, opportunity cost, returns to scale, currency conversion, trade protection, and NNI.

The total value of goods and services produced within a country's borders, regardless of the nationality of the producers, is defined as Gross Domestic Product (GDP).

The correct option is B.

$$\boxed{\text{B. Gross Domestic Product.}}$$

Opportunity cost is the value of the next best alternative foregone. If no alternative is sacrificed, then there is no opportunity cost.

The correct option is C.

$$\boxed{\text{C. no alternative is sacrificed.}}$$

When a firm doubles all its inputs and output more than doubles, this indicates that the firm is experiencing increasing returns to scale.

The correct option is C.

$$\boxed{\text{C. increasing returns to scale.}}$$

To find the cost in FCFA, multiply the cost in Euros by the exchange rate.
Cost in FCFA = $350 \text{ Euros} \times 675 \text{ FCFA/Euro}$
Cost in FCFA = $236,250 \text{ FCFA}$

The correct option is C.

$$\boxed{\text{C. 236,250 FCFA.}}$$

Trade restrictions, such as tariffs or quotas, are primarily implemented to protect domestic industries, especially new or developing ones (infant industries), from foreign competition.

The correct option is D.

$$\boxed{\text{D. protect infant industries.}}$$

Net National Income (NNI) is calculated by subtracting capital consumption (depreciation) from Gross National Product (GNP).

The correct option is B.

$$\boxed{\text{B. Capital consumption.}}$$

A reduction in advertising cost per unit as output increases is a type of marketing economy of scale, as advertising is a marketing expense.

The correct option is C.

$$\boxed{\text{C. marketing economies.}}$$

An indirect tax is a tax levied on goods and services rather than on income or profits. Value Added Tax (VAT) is an example of an indirect tax.

The correct option is A.

$$\boxed{\text{A. Value added tax.}}$$

In developing countries, a significant problem facing agriculture is the lack of adequate storage facilities, which leads to post-harvest losses.

The correct option is C.

$$\boxed{\text{C. poor-storage facilities.}}$$

Total utility is the sum of marginal utilities.
Total utility for 3 units = MU(1) + MU(2) + MU(3)
Total utility = $4 + 3 + 2 = 9 \text{ units}$

The correct option is A.

$$\boxed{\text{A. 9 units.}}$$

The main purpose of a stock exchange is to provide a regulated market for buying and selling securities like stocks and bonds.

The correct option is D.

$$\boxed{\text{D. provide a market for securities.}}$$

Inflation is a general increase in prices and a fall in the purchasing value of money. Therefore, a negative effect of inflation is that it reduces the real value of money.

The correct option is D.

$$\boxed{\text{D. reduces the real value of money.}}$$

Education and skills are considered components of human capital, which is classified as human wealth.

The correct option is B.

$$\boxed{\text{B. human wealth.}}$$